1. Field of the Invention
The present invention relates to an illuminating device for an instrument of an automotive vehicle, aeroplane, ship, or the like.
2. Description of the Prior Art
An automotive vehicle or the like is equipped with instruments in the instrument panel in front of the driver's seat such as a speed meter, a fuel indicator, a thermometer for indicating the temperature of the cooling water and other various meters and indicators.
As for an example, FIG. 1 shows an arrangement of the instruments in the instrument panel generally indicated the Roman reference numeral I in the front of a cabin of a vehicle or the like. The instruments are mounted inside the instrument panel located below the windshield 5. In front of the instrument panel, indicating plates or dials 1 of the meters, such as a speed meter, fuel indicator, thermometer and other various meters are equipped.
FIG. 2 shows a cross-sectional view of such an instrument panel of the conventional type. The conventional illuminating device is substantially as shown in FIG. 2. Namely, an internal light source 3 such as a lamp is arranged inside the instrument I so as to illuminate an indicating element of the indicating plate or dial 1 formed by a light transmissive plate such as a transparent plate or a liquid crystal panel so as to clearly show the indication appearing on the dial 1 even in a dark place at night.
In such a conventional illuminating device for an instrument, the indicating portion of the indicating plate or dial 1 may be illuminated to show clearly by the internal light source 3 at night time when the vehicle light is turned on. However, at day time when the internal light source is not switched on, the indication on the dial 1 should be confirmed by the day light in the cabin. In this case, the pupil of the driver varies mainly depending on the brightness of the front view or scenery. Accordingly, in case the front view is very bright scenery compared with the light in the cabin, such as for instance, on a very fine day, the driver may feel difficulty in identifying the indication on the dial or it might be invisible momentarily when the driver turns his eye upon the indicating panel or dial.